Low background detector with enriched 116CdWO4 crystal scintillators to search for double beta decay of 116Cd

TL;DR

This study developed a low-background detector using enriched $^{116}$CdWO$_4$ crystals to search for double beta decay, involving crystal growth, characterization, and underground testing to assess radiopurity and sensitivity.

Contribution

The paper presents the first implementation of a low-background detector with enriched $^{116}$CdWO$_4$ crystals for double beta decay search, including detailed radiopurity assessment and sensitivity estimation.

Findings

Crystal radiopurity levels were successfully estimated.

The detector demonstrated low background levels underground.

Sensitivity to double beta decay was quantified through simulations.

Abstract

A cadmium tungstate crystal boule enriched in $^{116}$Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two $^{116}$CdWO$_4$ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third $^{116}$CdWO$_4$ sample (326 g) was tested with the help of ultra-low background high purity germanium $\gamma$ detector. Monte Carlo simulations of double $\beta$ processes in $^{116}$Cd were used to estimate the sensitivity of an experiment to search for double $\beta$ decay of $^{116}$Cd.